A second family of letter beacons includes those operating outside the clusters. For this reason they are often called "Solitary beacons" or "Solitaires". These beacons also transmit their single-letter identifier in standard CW (A1A) using Morse code.

A second family of letter beacons includes those operating outside the clusters. For this reason they are often called "Solitary beacons" or "Solitaires". These beacons also transmit their single-letter identifier in standard CW (A1A) using Morse code.

-

A few solitary beacons, like "R" on 4325.9 and 5465.9&nbsp;kHz, operate exactly like the cluster beacons, sending only their single letter identifier. <sup>(20)</sup>

+

A few solitary beacons, like "R" on 4325.9 kHz and 5465.9&nbsp;kHz, operate exactly like the cluster beacons, sending only their single letter identifier. <sup>(20)</sup>

The majority of solitary beacons, and most notably "P" on various MF and HF frequencies, most of the time transmit their single-letter identifier in morse code. However, occasionally the routine transmission is interrupted and brief messages are sent in fast Morse code or in an FSK digital mode. Therefore, the proper term for these beacon-like single-letter transmissions is "channel markers" <sup>(6) (15)</sup>, as their purpose is to occupy and identify a particular HF transmission channel when no traffic is transmitted. There is no evidence that the cluster beacon "P" and the solitary beacon "P" are directly related.

The majority of solitary beacons, and most notably "P" on various MF and HF frequencies, most of the time transmit their single-letter identifier in morse code. However, occasionally the routine transmission is interrupted and brief messages are sent in fast Morse code or in an FSK digital mode. Therefore, the proper term for these beacon-like single-letter transmissions is "channel markers" <sup>(6) (15)</sup>, as their purpose is to occupy and identify a particular HF transmission channel when no traffic is transmitted. There is no evidence that the cluster beacon "P" and the solitary beacon "P" are directly related.

Revision as of 20:40, 11 January 2019

Letter Beacon D on 5153.7 kHz

A Letter beacon (or single letter beacon) is a high frequency (HF) radio transmission of uncertain origin, which consists of only a single repeating Morse Code letter.

These transmissions sre often referred to as:

"Letter beacons"

SLB, or "Single Letter Beacons"

SLHFB, or "Single Letter High Frequency Beacons", the original SPEEDX designation.

History

The letter beacon radio transmissions were discovered in the late 1960s but were known only to a few specialized DXers. Their presence became known to the wider amateur radio community in 1978, when beacon “W” started transmitting on 3584 kHz, in the 80 meters band. SPEEDX published indirect evidence that this particular transmitter was located in Cuba. (3)

In 1982 SPEEDX reported, supposedly on the basis of HF direction finding by the US military, that beacon “K” transmitting on 9043 kHz was located at 48° 30' N - 134° 58' E, near the city of Khabarovsk in the USSR. (4), (5) A few years later, W. Orr, W6SAI, suggested that the "K" beacons were actually located at Petropavlovsk on the Kamchatka Peninsula and the "U" beacons were located at the Barents Sea coast, between Murmansk and Amderma. (6)

Location of letter beacons

According to Schimmel, in 1986 the FCC released the following HF direction finding results for single letter beacons, all of which indicate locations in the USSR: (5)

ID letter

Location

C

Moscow, RUS

D

Odessa, UKR

O

Moscow, RUS

P

Kaliningrad, RUS

S

Arkhangelsk, RUS

U

Between Murmansk & Amderma, RUS

Z

Mukachevo, UKR

The link with the USSR and, more recently, Russia is further supported by the existence of single letter beacons transmitting letters existing only in the Cyrillic morse code alphabet, like the Ю beacon (22) which operated on 13627 and 13639 kHz in the early 1980s.

The ENIGMA group also accepted these locations for cluster beacons "C", "D", "P" and "S", adding Vladivostok for beacon "F". (7)
A recent source (2006) regarding locations was published on the Web by Ary Boender.(8)(24) This publication also contains an extensive list of frequencies of letter beacons, both current and historical. The following locations are stated for cluster beacons:

ID letter

Callsign

Location

A

Astrakhan, RUS (tentative)

C

Moscow, RUS

D

Sevastopol, UKR

F

Vladivostok, RUS

K

RCC

Petropavlovsk-Kamchatsky, RUS

L

Unknown, appeared on July 1, 2011

M

RTS

Magadan, RUS

P

RMP

Kaliningrad, RUS

S

RCV

Severomorsk, RUS

For solitary beacons and markers, Boender suggests these locations:

ID letter

Location

L

Tirana, ALB (defunct)

R

Izhevsk (Ustinov), RUS

P

Kaliningrad, RUS

V

Khiva, UZB or Almaty, KAZ (25)

Transmissions of the "P" beacon in December 2007, even on medium frequency (420 and 583 kHz) indicate the Russian Naval Base of Kaliningrad as a possible source. (9) Kaliningrad officially uses the ITU registered callsign RMP. The identity of "P" beacon as an alias for RMP was first discovered by Ary Boender in 1995, when it transmitted RTTY weather forecast for Baltic Sea using callsign RMP on 3262 kHz [1].

Types of letter beacons

The single letter beacons are currently classified in two groups, the "Cluster beacons" and the "Channel markers". A beacon "P" exists in both groups. A third group, the FSK beacons, is now extinct. The following sections list the beacons currently (July 2010) active, according to published listeners’ reports.

Cluster beacons

A group of radio beacons with single-letter identifiers ("C", "D", "M", "S", "P", "A", "M" and "K") have been regularly reported in small spectrum segments centered around 3594 kHz, 4558 kHz, 5154 kHz, 7039 kHz, 7509 kHz, 8495 kHz, 10872 kHz, 13528 kHz, 16332 kHz and 20048 kHz. The term "cluster beacons" is frequently used for them, as these beacons transmit in parallel on frequencies only 0.1 kHz apart. These beacons transmit only their single-letter identifier in standard CW (A1A) using morse code.

Occasionally some cluster beacons (especially "F" and "M") have been reported transmitting on frequencies different from their regular channel for short periods.

Solitary beacons and channel markers

A second family of letter beacons includes those operating outside the clusters. For this reason they are often called "Solitary beacons" or "Solitaires". These beacons also transmit their single-letter identifier in standard CW (A1A) using Morse code.

A few solitary beacons, like "R" on 4325.9 kHz and 5465.9 kHz, operate exactly like the cluster beacons, sending only their single letter identifier. (20)

The majority of solitary beacons, and most notably "P" on various MF and HF frequencies, most of the time transmit their single-letter identifier in morse code. However, occasionally the routine transmission is interrupted and brief messages are sent in fast Morse code or in an FSK digital mode. Therefore, the proper term for these beacon-like single-letter transmissions is "channel markers" (6) (15), as their purpose is to occupy and identify a particular HF transmission channel when no traffic is transmitted. There is no evidence that the cluster beacon "P" and the solitary beacon "P" are directly related.

It was reported in Numbers and Oddities, issue 142, that beacon C on 8000 kHz also transmitted messages under the regular callsign RIW, which is allocated to a Russian naval communications station in Khiva, Uzbekistan. (11)

There are also a few oddities, transmitting signals with poor modulation and irregular timing, like "V" on 5342 and 6430.7 kHz.

Channel marker "W", which appeared in 2012, is possibly related to a net for Russian Air Force Tu-95MS Bear H strategic bombers.

FSK beacons

This group included the "K" and "U" beacons, which are no longer active. They transmitted their morse code single letter identification by shifting the frequency of the carrier by approximately 1000 Hz. This mode of "FSK-CW" has the ITU designation F1A. The use of FSK indicated that the transmitter was suitable for FSK data transmissions, like RTTY.(26)

ENIGMA designation

Chris Midgley and Mike Gaufman of ENIGMA devised a naming scheme for all stations in their sphere of interest. In the original scheme, the following identifications were issued to letter beacons: (13)

ENIGMA ID

Description

MX

Cluster beacons

MXV

Irregular “V” beacons, not in clusters

MXS

Solitaires: letter beacons out of cluster bands

MXF

FSK beacons (K, U), no longer active in 1995

ENIGMA-2000, the internet based ENIGMA successor group, revised the original ENIGMA designators. The current designations for letter beacons are the following (since 2007):(14)

ENIGMA ID

Description

MX

Solitary HF single letter beacons

MXI

Single letter beacons in clusters

MXII

FSK beacons (K, U), no longer active

MXV

Irregular “V” transmissions

MXP

Letter beacons also sending messages

MXIII

(deleted, merged with MX)

MXIV

(deleted, merged with MX)

Purpose of letter beacons

The purpose and the applications of letter beacons are not yet known with certainty. Many theories and speculations have appeared in specialized bublications, but none is based on documentary evidence. They have been postulated to be radio propagation beacons, channel markers, used in tracking satellites, or used for civil defense purposes. (15) Some stations of this family, in particular the “U” beacon, have been implicated in deliberate jamming. (16)

Today the radio propagation beacon theory is generally accepted for the cluster beacons. According to ENIGMA the cluster beacons are used by the Russian Navy (and especially the submarine branch) to find the most suitable radio frequency for contact based on current radio propagation conditions. (7)

Similar systems

QSL card from a USCG beacon with signle letter ID

A few aero navigation Non Directional Beacons (NDBs) and marine beacons also transmit single letter identification codes. They can be easily distinguished from Letter beacons as they transmit in the allocated low frequency and medium frequency bands, most of them are listed in appropriate aviation handbooks and their transmission mode is A2A (full carrier with audio modulation).

Some High Frequency Beacons also transmit a single letter as identification. On September 7, 2010 a beacon was heard on 9111.7 kHz at 1546 UTC. It sent a slow marker "A", which did not sound like a Russian beacon (MX). It sounded like somebody was playing with the key sending letters "A" and "M". Transmission lasted untill at
least 1630 UTC. (19)

See also

Notes & References

ENIGMA stands for "European Numbers Information Gathering and Monitoring Association". It was a unique association of radio listeners based in the United Kingdom and operated during the 1990’s.

ENIGMA2000 is an internet based community with the same general interests as the old ENIGMA association and with wider coverage of general Intelligence matters. This group produces a regular newsletter and maintains the old ENIGMA station naming scheme. ENIGMA-2000 shows less interest in letter beacons than its predecessor.

I doubt that "R" is a Navy service. The distance from Izhevsk (formerly Ustinov) to the nearset sea coasts is 1200 km. Only low frequencies are in use (3194//3321//4325) for 24 hrs operations. How could it reach ships in local daytime? Unlike clusters, it is not a propagation or navigation beacon. Unlike single "P" (RMP-Kaliningrad) naval station, it does not transmit any RTTY or CW messages. It is more similar to "The Pip" (3757;5448). In both cases, transmissions consist of a single letter (marker) in CW, and of short SSB voice messages, most probably for checking a readiness of network operators. I think that both "R" and "XP" are similar communications stations of Staffs of military districts (voenny okrug) of the Russian Army. The reliable coverage area would be up to 500 km, at least in local daytime.

Cluster beacon "L" appeared on 7038.2 and 8494.2 kHz and was was first reported by the VERON Intruder Watch on June 29, 2011 at 1800 UTC. "L" was also active throughout July 2011. The first thoughts were that "L" transmitted from St Petersburg but so far there is no evidence to support this. It moved on July 23, 2011 to 7041.6 and 8497.9 kHz and again on July 24, 2011 to 7041.8 and 8497.8 kHz. (Ary Boender: "Number and Oddities", issue 166, pp.7). Cluster beacon "L" is not the solitary letter beacon "L" that transmitted in the past from Tirana, Albania, given that Albania is now a member of NATO. At the same time, the 10 MHz "P" beacon moved 1 kHz up, from 10871.8 to 10872.8 kHz.

A couple of years ago I had the chance to speak to a Russian naval radio operator who works on a Russian frigate. He confirmed to me that the channel markers are military stations, mostly used by the navy. His English was poor so I could not ask for more detailed info, and as I don't speak Russian, you can imagine that it was a really nice conversation. I had to write down the morse characters of the call signs of the stations and he told me the locations. It was really fun, believe me :-) A couple of the markers that he mentioned have now disappeared but still exist as cluster beacons. The radio operator identified 'L' as St.Petersburg, 'P' as Kaliningrad (HQ of the Baltic Fleet), 'S' as Arkhangelsk and 'C' as Moscow (naval HQ). He knew that there were more stations but didn't know which ones because they were not relevant for his vessel.Ary Boender: "32nd edition of the N&O column / Spooks newsletter", December 24, 2000 [2].

External links

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